A battery pack that is repeatedly used and charged by a charger is used in a state of being connected to any of various connected devices, such as a charger or a power consumption element.
Since there is generally no way to directly measure the remaining battery charge of a battery pack, it is estimated using a measurement history or the like in which changes in physical quantities such as voltage, current, impedance, and temperature are recorded.
For example, Patent Literature 1 discloses a battery pack management system in which, if the SoC of a battery estimated using the charging and discharging current, the battery voltage, the battery temperature, and so forth is less than or equal to a reference SoC, then a reference remaining capacity, the current battery voltage, and so forth are used to estimate the current SoC.